Field scale flow processes and soil water dynamics in seasonal wetlands of the Canadian Prairies

English Abstract:

The Canadian Prairies are characterized by hummocky terrain containing numerous depressions and wetlands with complex hydrological systems. Quantifying hydrological processes is challenging as a result of the intricate relationships between surface flow, interflow and groundwater flow. Northern hydrology is further complicated by a seasonal freezing component that can lead to large variations of near surface and surface fluxes which dominate soil water redistribution in the unsaturated zone. We couple intensive field monitoring and numerical modeling to investigate the seasonal dynamics of soil water variability and groundwater flow direction at a wetland field site in the Saskatchewan Canadian Prairies. Soil water content, matric potential and soil temperature are monitored continuously within the top three meters of the unsaturated zone along a transect located between two terminal monitoring ponds. Water levels are monitored via nested piezometers located at the center of each of the terminal ponds and along the monitoring transect. We have used field observations to develop a numerical flow model based on Richards’ equation coupled with a frozen soil infiltration algorithm to simulate unsaturated-saturated flow and examine the contribution of snowmelt infiltration in the spring. The interaction of subsurface flow and terminal wetland ponds along with observed water table responses is presented. This study provides valuable insights into field scale flow processes and soil water dynamics within the Canadian Prairies unsaturated zone.